1. Field
This invention relates to support systems suitable for treating the blood of a patient outside of the body and returning the blood to the body as part of a medical treatment or life support activity
2. State of the Art
Today a variety of medical treatments involve procedures by which the blood of a patient is processed through an external or extra corporeal system. For example, the blood may be removed for dialysis or for oxygenation.
In the same vein, various surgical procedures involving the heart may require diversion of the blood from the cardio-pulmonary system until completion of the involved surgical procedures.
Systems for extra corporeal support of a patient are known. For example U.S. Pat. No. 4,662,355 (Pieronne) discloses a pump regulation system which may be used for regulation of the bypass circuit of an artificial kidney and a cardio-pulmonary system. Various components for use in such systems are available commercially. For example, Seabrook Medical Systems, Inc. of the Cincinnati, Ohio offers a blood warming unit for warming the blood before it is returned to the patient and a bladder holder for use as an inlet reservoir for a pump. Seabrook Medical Systems, Inc. also offers a pump controller as well as a cart for mounting or positioning selected components of an extra corporeal support system.
Canyon Medical Products of Salt Lake City, Utah offers percutaneous femoral by-pass cannulation systems which may be suitable for interconnecting extra corporeal support systems to a patient. Stockert-Shiley of Irvine, California offers pressure control modules for use in extra corporeal support systems. C.R. Bard, Inc. of Billerica, Massachusetts even offers a complete extra corporeal cardio-pulmonary support system as a commercial product.
Commercial components and systems available today have typically been available for adult patients and some infants. Newborns may need temporary cardio-pulmonary support when suffering respiratory failure or a fulminant disease leading to respiratory failure. Extra corporeal support for newborns (neo-nates) has been successfully employed for over 10 years. The procedure has been described in several professional journals. R. H. Bartlett, et al., EXTRA CORPOREAL MEMBRANE OXYGENATION (ECMO) Cardio-pulmonary SUPPORT IN INFANCY, Trans. Amer. Soc. Artif. Int. Organs, 1976, p. 80-93 (Vol. XXII); R. H. Bartlett, et al., EXTRA CORPOREAL CIRCULATION (ECMO) IN NEO-NATAL RESPIRATORY FAILURE, Jnl. of Thor. and Card. Surgery, 1977, p. 826-33 (Vol. 74, No. 6); L. Gattinoni, et al., REVERSAL OF TERMINAL ACUTE RESPIRATORY FAILURE BY LOW FREQUENCY POSITIVE PRESSURE VENTILATION WITH EXTRA CORPOREAL REMOVAL OF CO.sub.2 (LFPPV-ECCO.sub.2 R), Trans. Am. Soc. Artif. Internal Organs, 1981, p. 289-93, (Vol. XXVII); and W. Fukui, et al., A PORTABLE, PUMPLESS, AV BY-PASS ECCO.sub.2 R SYSTEM WITH A HOLLOW FIBER MEMBRANE LUNG, 1986, Tran. Soc. Artif. Internal Organs, p. 521-24 (Vol. XXXII).
Extra corporeal support for neo-nates is monitored by a national central registry. It now has recorded data for over 1800 patients receiving such treatment. Notably, newborns have rather small blood volume (e.g. 1 liter or less) and are therefore quite difficult to treat because an external support system requires a volume of blood to work. Further, any extra corporeal support system inherently involves the use of substantial amounts of heparin in order to minimize clotting, not only in the system but also internally within the patient. As a result, it is presently understood that extra corporeal support of neo-nates has been limited to those weighing approximately more than 2 kilograms and who are typically more than 35 weeks gestation at birth. Nonetheless, there are a considerable number of neo-nates who are candidates for extra corporeal support, but who are not of sufficient size to successfully undergo treatment.
It is presently understood that many of the neo-nates who qualify for the treatment are inherently poor risks for transport. Nevertheless, many of the neo-nate patients reported to the national central registry were born away from the treating center and were necessarily transported. Under these circumstances, there is a compelling and growing need for an extra corporeal support system to deal with neo-nates presently untreatable and to improve the ability to transport all neo-nates. That is, there is a need for a more regulated, automated and more transportable extra corporeal support system. Notably, such a system would also be suitable for use not only with neo-nates but also with older patients, particularly those requiring transport. Further, a highly automated system may be desirable for use with all patients, regardless of age, because of the reduced involvement of attendant personnel, in for example, an intensive care unit (ICU). Additionally, a smaller and more compact system is desirable to reduce or minimize the risks of contamination from a larger system. The increased need for heparin and the increased potential for hemolysis.
Efforts heretofore to miniaturize have been attempted. T. Kawamuri et al., EXTRA CORPOREAL MEMBRANE OXYGENATION (ECMO) IN PUMPLESS RIGHT VENTRICLE TO LEFT ATRIUM BY-PASS, 1985 Trans. Am. Soc. Artif. Intern. Organs, p. 616-620 (Vol. XXXI). The reported miniaturized system used the pressure gradient between the arterial and venus systems. However, in many circumstances, particularly in the context of an asphyxiated myocardium, such a pumpless system is believed to be inapplicable or unsuitable. Further, the devices described did not appear to be suitable for long use and became routinely nonfunctional after 24 to 48 hours when in typical neo-nate applications, the extra corporeal support may be required for periods up to 130 hours, if not more.